Performance of an insect-proof screen as covering material in a greenhouse with improved opening surface.

摘要

Pollution caused by the use of pesticides has become a major concern in today's horticultural production. Insect-proof nets over vents can lower the use of insecticides in greenhouses, yet they hinder air exchange, causing high temperature problemsin Mediterranean countries. A compromise between acceptable natural ventilation and pest protection can be found if the area of the greenhouse openings is increased. This article compares the internal climate, air exchange rate, pest incidence and crop response in a greenhouse with 50% of the roof surface covered by an insect-proof screen with those of another unscreened commercial greenhouse with smaller opening surface. Both greenhouses maintained similar climatic conditions. The air exchange rate wasslightly less in the greenhouse with improved opening area and insect proof screen. There were no significant differences in growth, production and quality of Gerbera jamesonii in either greenhouse. The most positive result was that the insect-proof mesh clearly reduced the population of whiteflies, heliothis and leaf miners. A significant reduction in the number of pesticide applications was achieved without worsening the internal climate and crop response. However, the insect net was not an effectivebarrier against Frankliniella occidentalis. For this purpose a thicker net would have been required, but air exchange measurements with this net showed that ventilation is not sufficient to have an adequate internal climate.